Broadcast and multicast communications are a form of point-to-multipoint communications wherein information is simultaneously transmitted from a single source to multiple destinations. The third generation partnership project long term evolution (“3GPP LTE”) is the name generally used to describe an ongoing effort across the industry to improve the universal mobile telecommunications system (“UMTS”) for mobile communications to cope with continuing new requirements and the growing base of users. The goals of this broadly based project include improving communication efficiency, lowering costs, improving services, making use of new spectrum opportunities, and achieving better integration with other open standards. The term multimedia broadcast and multicast service (“MBMS”) is 3GPP terminology that refers to broadcast and multicast services and related systems associated therewith.
A single frequency network (“SFN”) is a transmission mode in long term evolution multimedia broadcast and multicast service wherein several transmitters simultaneously transmit the same signal over the same frequency channel. A single frequency network is also called a multicast broadcast single frequency network (“MBSFN”) or multi-cell point-to-multipoint (“multi-cell PtM”) mode. Thus, single frequency network operation implies content synchronization of base stations transmitting a multimedia broadcast and multicast service within an associated deployment area, for instance, within a cyclic prefix length of a few microseconds, as seen by user equipment receiving the multimedia broadcast and multicast service from the base stations. (See, e.g., 3GPP TR R3.018, entitled “3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved UTRA and UTRAN; Radio Access Architecture and Interfaces (Release 7),” Version 0.7.1 (February 2007), which is incorporated herein by reference.)
The UMTS terrestrial radio access network (“UTRAN”) is a part of a UMTS communication network that includes one or more radio network controllers (“RNCs”) and one or more nodes. An evolved UTRAN (“E-UTRAN”) provides new physical layer concepts and protocol architectures for the UMTS. While the discussion that follows is directed to multimedia broadcast and multimedia multicast services for a 3GPP LTE E-UTRAN employing single frequency network transmission, the concepts as described herein are applicable to any multimedia broadcast communications and communication networks, in general.
The multimedia broadcast and multimedia multicast services often operate with a synchronized single frequency network. In the event that a service provider wishes to provide nationwide service and does not form a nationwide single frequency network, the service can instead form localized single frequency networks from multiple cells, and then form a nationwide broadcast network from the multiple localized asynchronous single frequency networks. In this arrangement, the same multimedia broadcast and multimedia multicast services are provided in every localized single frequency network. Issues arise, however, when user equipment moves between single frequency networks. The issues that arise are similar to those that currently exist in analog broadcast television, wherein users change channels or frequencies when moving across the border of two broadcast areas. This limitation is much more pronounced in multimedia broadcast and multimedia multicast services for 3GPP LTE E-UTRANs, as one single frequency network area therein is typically smaller than a conventional digital/analog broadcasting service coverage area. Additionally, issues arise in connection with controlling dynamic single frequency networks or controlling the participation of individual cells in a single frequency network based on locally varying service demand (i.e., user equipment wishing to receive the service). The problem stems from the luxury of having an uplink channel available in conjunction with the broadcast network.
Accordingly, what is needed in the art is a system and method that controls base stations for multimedia broadcast communications, especially for multimedia broadcast and multimedia multicast services for 3GPP LTE E-UTRANs employing a single frequency network.